The present invention relates to a method for manufacturing a rigid, perforated cloth or fabric.
It is well known in the art to adapt woven fabrics as filter elements for filtering particulate matter from a liquid or gaseous fluid as that fluid passes across the woven fabric filter element. Such filter elements have been produced from woven metallic wire; however, filters so produced suffer the disadvantage that they cannot be used for the filtration of chemical compounds with which the metal of the wires is prone to react.
Woven fabric filter elements have also been made from monofilament of synthetic materials such as, for example, polyester. However, these filter elements suffer from shortcomings essentially inherent to the ability of the synthetic monofilaments to stretch, thus limiting their use to working pressures below the irreversible elastic deformation limit of the synthetic materials.
It has been proposed to manufacture filter fabrics from glass yarns, but such filters, because of the transverse fragility of the elementary glass filaments, show poor resistence to abrasion by the materials to be filtered and accordingly deteriorate rapidly.
In order to overcome these and other shortcomings, it has been proposed to coat the filter fabric material with a suitable thermoplastic polymer. However, this technique has not been entirely satisfactory because such technique is delicate to carry out, requires specific apparatus to coat the fabrics with an appropriate polymer and, finally, does not provide for satisfactory control in the way the individual yarns comprising the fabric network are bonded together, thereby producing deformation of the fabric network which adversely affects the filtering capacity of the woven fabric filter.
It has also been proposed to produce woven fabrics from yarns previously coated with a sleeve of plastic by weaving the coated yarns into a fabric network and thereafter heating the fabric by, for example, hot calendering, in order to bond the yarns to each other at their points of intersection. Such procedures are more specifically described in French Pat. Nos. 1,041,697 and 1,502,610. Unfortunately, this technique, which is satisfactory for the manufacture of fabrics for window blinds and curtains, requires special equipment, precise operation and considerable time in which to make the woven fabric.